Battery Management Systems
Contents
Cell Balancing Methods
Active Cell Balancing
Passive Cell Balancing
Safety and Monitoring
As lithium and some other battery chemistries can be quote volatile when outside of their operating range, it is important of a battery management system to be able to sufficiently measure properties like temperature and voltage of individual cells. This data can also be used to feed algorithms that provide insight like state-of-charge estimation.
Typical Cell Safe Operating Ranges
| Chemistry | Min Voltage | Max Voltage | Discharge Temperature | Charge Temperature |
| Li-Po | 3.0V | 4.2V | 10°C ~55°C | 5°C ~ 45°C |
| LiFePO4 | 3.0V | 3.6V | -20°C ~ 60°C |
0 ~ 55°C |
Temperature Measurement
As per FS rules and industry good practice, a significant number of cells should have their temperature measured often to ensure safety preventing such events like thermal runaway from occurring.
Typically this is done by placing a thermistor on the negative terminal of the cell with a thermally conductive, but electrically insulative material in-between for purposes of isolation.
Voltage Measurement
To ensure cells are not being over charged or discharged, accurate voltage measurement of each cell is needed. The battery management system only needs to measure each series connected cell as parallel connected cells will always have the same voltage potential.
